Electrostatic recording apparatus and method

ABSTRACT

An electrostatic copying device including a donor roller for supplying a layer of toner and a photoreceptor drum and associated components for generating a latent image are operated in consort in a two-rotation cycle of operation under controlled condition. During the first rotation of the cycle of operation the photoreceptor is uniformly charged with a relatively low corona charge and the photoreceptor is used as a biased roller to make uniform the layer of toner placed on the donor roller. During the second rotation of the cycle of operation the latent image is generated and the latent image is developed using the uniformly made toner layer.

United States Patent 1151 3,697,169 Maksymiak et a]. [4 Oct. 10, 1972 [54] ELECTROSTATIC RECORDING 3,375,806 4/1968 Nost ..355/3 X APPARATUS AND METHOD [72] Inventors: John Maksymiak, Penfield; Kenneth Primary Exammer samuel Matthews M. Beach, Jr., Webster; James W. Smith, Fairport, all of NY.

[7 3] Stamford,

Xerox Conn.

Filed: Jan. 6, 1971 Appl. No.: 104,339

Assignees Corporation,

[56] References Cited UNITED STATES PATENTS 3,405,682 10/1968 King et al ..96/1.4 X 3,453,045 7/1969 Fantuzzo ..355/3 3,152,012 10/1964 Schaffert ..355/3 x Assistant Examiner-Fred L. Braun Attorney-James J. Ralabate, Donald F. Daley and Kenneth E. Merklen ABSTRACT An electrostatic copying device including a donor roller for supplying a layer of toner and a photoreceptor drum and associated components for generating a latent image are operated in consort in a two-rotation cycle of operation under controlled condition. During the first rotation of the cycle of operation the photoreceptor is uniformly charged with a relatively low corona charge and the photoreceptor is used as a biased roller to make uniform the layer of toner placed on the donor roller. During the second rotation of the cycle of operation the latent image is generated and the latent image is developed using the uniformly made toner layer.

17 Clairm, 1 Drawing Figure PATENTEDum 10 1972 CYCLIC v20 INVE R fl nmmwrmi cfim y AMES W. SMITH A T7D/PNEV ELECTROSTATIC RECORDING APPARATUS AND METHOD The present invention relates to electrostatic recording devices and in particular a novel method and apparatus for developing a latent image fonned on a photoreceptor drum.

It is well known to corona charge, as by a corotron driven by a direct current potential, a photoreceptor surface, such as a drum, for example, and apply like charges over the surface of the drum and to dissipate a pattern of those charges on the surface of the drum by illuminating the surface of the drum with a predetermined pattern and thereby form a latent image in the form of the retained charges. It is also known that the latent image may be developed into a visible image by applying a pigmented material, such as finely particlized carbon black or other pigment to the surface bearing the latent image so that the retained charges may attract and secure the pigmented material and thus provide a visible image of the predetermined pattern. It is also known in the art to transfer the visible image from the photoreceptor to a substrate, such as paper, for example and to fuse the pigmented material to the substrate to form a permanentized copy or recording of the predetermined pattern. One domestic patent which teaches the above is US. Pat. No. 3,062,095 issued to Rutkus, Jr. et al. a I

Another domestic US. Pat. No. 2,895,847, issued to Mayo taught the use of a donor member which is loaded with a coating of pigmented material and by contacting the surface of the photoreceptor, the pigmented material hereinafter referred to as toner develops the latent image on the photoreceptor. The domestic US. Pat. No. 3,232,190 issued to Willmott taught that when a donor member is coated with toner, development of a latent image may be made with the donor member and the photoreceptor in spaced relation.

.The apparatus and methods employed for out-ofcontact (spaced) development using a donor member to supply toner as a coating or layer on the surface of the donor member to the photoreceptor are complex and require spacings of very tight tolerance. The forming of a coating or layer of toner having uniform characteristics also offers several problems.

The present invention greatly advances the art and 'greatly contributes to electrostatic recording device by providing novel methods and apparatus embracing electrostatic recording methods and apparatus particularly employing the out-of-contact development technique using substantially less apparatus while providing a uniform coating i.e. layer of toner on the donor member and effectively reducing the tight tolerance with respect to spacing between the donor member and the photoreceptor. By employing control apparatus one of the components in the electrostatic recording device serves a dual function, essentially eliminating other heretofore employed hardware.

Although an embodiment of the present invention and the description of the invention presented herein embraces the out-of-contact development technique, the present invention may also be employed using actual (physical) contact development techniques. It will be appreciated that the latter system, i.e., actual contact development itself avoids the problem of uniform spacing between the donor member and the photoreceptor but other problems such as the presence of agglomerates on the toner coating of the donor member and/or non-uniform coating of the donor member still remain and are overcome by use of the present invention.

Briefly, the apparatus of the present invention includes a donor member, such as a donor roller with a means of supplying toner to the surface of the donor member. This may be done by using a toner bath and rotating the donor roller through the toner bath. The toner bath, for the purposes of the present invention is removable, in accordance with the phase of the cycle of operations as controlled by a cyclic controller. The donor roller also includes a cleaning means for cleaning the surface of the roller in accordance with the phase of the cycle and a charging corotron, for corona charging the toner of the layer of toner on the surface of the donor roller. The apparatus also includes a photoreceptor, such as a photoreceptor drum and drive means such as a motor. Both the donor drum and the photoreceptor drum are preferably the same diameter, are driven in unison, at the same speed in different rotational directions. The present embodiment shows the photoreceptor driven in a clockwise direction and the donor member driven in a counter-clockwise direction. The photoreceptor drum has associated therewith a decharge corotron and photoreceptor surface cleaning apparatus, a charging corotron which corona charges the surface of the photoreceptor, a means of illuminating the charged surface of the photoreceptor for forming a latent image, an area at which development of the latent image occurs and a means for transferring the tonerized image to a substrate, such as paper, glass, plastic, etc. for preserving the tonerized image. The charging corotron may be a dual corotron or may be two separate corotrons, one for corona charging the surface of the photoreceptor with a relatively low power or weak power direct current charge, for example to volts DC and the other corotron for corona charging the surface of the photoreceptor with a relatively high power or strong power direct current charge, of the same potential direction, for example 400 to 500 volts DC.

The dual charging corotron or both charging corotrons, if two are employed, the illuminating means and the transfer means associated with the photoreceptor drum and the toner bath tray and the decharge corotron of the donor member are all under the control of a two phase cycle of operation controller or control means which functions in coordination with the rotation of the donor roller and the photoreceptor drum. The photoreceptor decharge corotron and the photoreceptor surface cleaning apparatus preferably function independent of the two phase control means so that the surface of the photoreceptor is clean prior to being corona charged by the charging corotron, regardless of the phase of the cycle of operation.

The cycle of operation, as controlled by the cyclic controller, is preferably a two phase cycle. Each phase of the cycle of operation is equal to one full rotation of the photoreceptor drum as sensed by a sensing means. During the first phase of the cycle of operation the cyclic controller is functioning in its phase 1 condition. During phase 1 the low power function of the photoreceptor drum charging corotron is energized and the high power function is de-energized while the illumination function is held de-energized. The decharging corotron of the donor member is energized during phase 2 to prepare the surface of the donor roller for cleaning after development of the latent image. The toner bath tray is in an up position, here considered to be a normal position, for purposes of description and the transfer apparatus is in an inactive or de-energized condition also considered a normal condition for descriptive purposes.

Thus, during the first cyclic rotation or phase .1 of the cycle of operation, the donor member is rotated through the toner bath, the surface being loaded with toner. It should be kept in mind the output control of the cyclic controller is provided in the particular phase of the cycle of operation and timed in accordance with the rotational position of the operating component with respect to the function to be provided. During phase 1 the decharge corotron of the donor member functions so that the old toner can be removed and a new or fresh coating of toner, can be applied to the surface of the donor member. The charging corotron may, if desired, be used to corona charge the new toner layer during phase 1 of the cycle only or, in the alternative may be used to charge thetoner layer during the whole of the operation. With respect to the photoreceptor drum, the decharge corotron and cleaning apparatus functions without regard to cyclic control since'it is desirable to always have the surface of the photoreceptor clean before corona charging occurs. During phase 1 of the cycle the low charge corotron is energized so that a low level charge is placed on the surface of the photoreceptor. The corona charge placed on the surface of the photoreceptor is preferably the reverse in polarity from corona charge placed on the layer of toner on the donor member. As the donor roller, with a fresh layer of toner and the photoreceptor drum, with a low corona charge on the surface rotate past each other, a portion of the layer of toner is transferred from the donor roller to the photoreceptor drum at the point or area at which development of the latent image normally takes place. This occurs because the entire surface of the photoreceptor, as it appears at the normal position of image development, is covered with a low power uniform electrostatic charge. This low power, uniform electrostatic charge has a power of attraction extending toward the surface of the donor roller, a uniform distance. Since the layer of toner on the donor roller may not be uniform in thickness the electrostatic charge on the photoreceptor captures toner from the thick portions of the layer. The amount of toner transferred between the rotating members depends upon amount (thickness) of the layer of toner thus the proximity of the toner on the donor roll to the photoreceptor surface and the magnitude of the corona charge on the surface of the photoreceptor.

Attracted to the surface of the photoreceptor drum will be weakly adhering toner and lumps and/or agglomerates which extend closer than the normal layer of toner to the photoreceptor surface. As the captured toner is conveyed, by the rotating photoreceptor past the de-energized transfer means the toner is presented to the decharge corotron and then to the cleaning apparatus where the toner is removed from the photoreceptor.

At the normal development point or area, where transfer of part of the layer of toner occurs a layer of toner is left on the donor roller, the layer being uniform in thickness, the thickness being adjustable in accordance with the magnitude of the low power corona charge placed on the surface of the photoreceptor and the spacing between the drum and roller surfaces.

The output of phase 1 of the cyclic controller is maintained for one complete revolution of the photoreceptor drum, which is rotating in unison with the donor roller. When the cyclic controller senses that the one revolution is complete the termination of the phase 1 output begins and institution of the phase 2 output starts. Due to this arcuate distribution of the components about the drum and roller, a timed termination of the phase 1' outputs and a timed actuation of the phase 2 outputs begins. Arcuately the preferred change of the phases is at the corotron charging point on the photoreceptor.

At the start of phase 2 of the cycle of operation, the power level of the corona charge is changed from relatively low power to relatively high power. As the area of relatively high power level of corona charge reaches the arcuate position where illumination occurs, the illumination function is activated. Thus a latent image is now formed on the surface of the photoreceptor drum.

In phase 2 the toner-bath tray is dropped away from the donor member so as to avoid distorting the uniform layer of toner created on the surface of the donor roller. The bath tray is held removed from toner contact with the donor roller surface for one full revolution of the donor roller. The decharge corotron associated with the donor roller is energized for one revolution, during phase 1 and then deenergized during phase 2 but the energization and de-energization thereof is timed so as not to interfere with the uniform created layer. The corona charge corotron for charging the layer of toner on the donor roller may be cyclically energized and deenergized if desired or may be held energized without regard to the cyclic operation.

When functioning in timed, phase coordination the start of the latent image onthe photoconductor drum and the start of the uniform layer of toner on the donor roller meetat the development point and the latent image is developed into a visible image as both components rotate. As the developed image reaches the transfer means the transfer means is actuated and the visible image is transferred to the substrate.

Thus it will be seen that while the donor roller makes two rotations in conjunction with the photoreceptor, the photoreceptor serves a dual function. During one phase or rotation of the cycle of operation the photoreceptor serves as a biased roller making a uniform layer of toner from a non-uniform layer of toner on the donor roller. During the subsequent phase of the cycle of operation the photoreceptor serves the normal function of a photoreceptor in an electrostatic recording device.

It is therefore an object of the present invention to provide an electrostatic recording device of the donor member photoreceptor combination in which the photoreceptor drum serves as a biased roller and a photoreceptor.

The FIGURE shows a preferred embodiment of the invention.

These and other objects of the invention will become apparent from reading a more detailed description of one embodiment of the invention embracing the principles set forth above, referenced to the drawing. The drawing represents an electrostatic recording device in which a donor member, such as donor roller driven in one direction, as indicated by arrow 11 and a photoreceptor l2 driven in the other direction as indicated by arrow 13 are spaced from each other, indicated as E. A motor and gear drive 14 drives both the photoreceptor drum, as by drive belts l5, and the donor roller, as by drive belts 16. Preferably the photoreceptor l2 and the donor roller 11 are driven in unison, that is at the same speed of rotation and at the same time, but in opposite directions.

Spaced arcuately about the surface of the photoreceptor drum to perform functions normally associated with the generation of an electrostatic record or copy of an original document or pattern is a decharge corotron or alternating current (AC) corotron represented by block A for discharging or neutralizing any charge on any toner that may be on the surface of the photoreceptor drum in preparation for cleaning the drum. Cleaning the surface of the drum 12 is accomplished by cleaning device represented by block B. Block C represents one or more corotrons which are employed to provide an electrostatic charge on the surface of the photoreceptor drum. As explained above the block C may represent one corotron in duplex array that may provide either of at least two different corona charge levels. So that as controlled by the cyclic controller, 20, the duplex array may provide a relatively low power DC corona charge as for example during phase 1 of the cycle of operation and may also provide a relative high power DC corona charge, as for example during phase 2 of the cycle of operation.

Block D represents the illumination function and may include a platen or other means for supporting or holding an original document or pattern, a light source and/or an optical system" which may project an image of the original document or pattern onto the surface of the photoreceptor to form a latent image through dissipation of the electrostatic charge on the surface of the photoreceptor drum in the pattern of the original document or pattern.

The illumination function is controlled by the cyclic controller 20. During phase 1 of the cycle of operation the illumination apparatus is held inoperative so that the relatively low corona charge deposited on the surface of the photoreceptor drum by the corotron C is maintained substantially uniform so that the function of a biased roller or drum may be performed by the photoreceptor drum. During phase 2 of the cycle of operation the illumination apparatus is activated under control of the cyclic controller so that the latent image, formed by the selective dissipation of the deposited relatively high corona charge on the surface of the photoreceptor, may be created.

The area of close proximity between the photoreceptor drum l2 and the donor roller 10 is indicated at E. At this area the layer of toner on the donor roller is made uniform and smooth by the limited captive power of the low power electrostatic charge on the photoreceptor during the phase 1 operation of the cycle of operation. During the phase 2 operation the latent a 6 image is developed by the. previously made uniform, smooth layer of toner on the donor roller.

The visible image, created by transaction of the toner, selectively relocated from the donor roller surface to the surface of the photoreceptor drum, according to the latent image formed by the electrostatic charge pattern, is transferred to a substrate such as paper or another carrier, for example by the apparatus represented at F. If desired the transfer apparatus, F may be operated independent of the phases of the cycle of operation. Thus, at each alternate rotation of the photoreceptor the visible image would be transferred to the substrate, for example during phase 2 of the cycle. During the other rotational period, phase 1, the substrate or carrier could be used to remove the toner captured in forming the uniform smooth layer of toner on the donor roller. This would reduce the work performed by the decharge (AC) corotron A and the cleaning apparatus B but this would unnecessarily use substantially twice the amount of carrier, such as paper, as normally used. Preferably, the visible image transfer apparatus is held inoperative during phase 1 of the cycle of operation and actuated during phase 2 of the cycle of operation.

The donor roller 10 has associated therewith a decharge (AC) corotron L shown energized by the phase 2 output of the cyclic controller 20 which functions to decharge or discharge the toner left on the surface of the donor roller after development of the latent image at area E. The toner remaining on the surface of the donor roller may be discharged in preparation for cleaning the surface of the roller prior to reloading the donor roller with a new layer of toner. During phase 1 the decharge corotron L is normally de-energized. To assist in'cleaning the surface of the donor roller is a blade scraper 21, mounted on the toner-bath tray assembly M. The toner tray holds the toner 22 and is pivotally mounted so that during phase 2 of the cycle the toner-bath tray is pivoted away from the surface of the donor roller. During phase 1 the tray is in its normal position, that is, in its up position so that the lower part of the donor roller 10 may pass through toner bath in the tray when the roller is rotated. The arrows 23 show how the toner-bath tray may be pivoted away from the lower surface of the donor roller 10.

Also associated with the donor roller is a corona charging corotron N for depositing a corona charge on the toner on the surface of the donor roller 10, prior to presentation of the toner layer to the development area E.

The cyclic controller may include therein a means of changing its output from phase 1 to phase 2 and then back to phase 1 for each successive rotation made by the uniformly rotated photoreceptor drum and donor roller. The cyclic controller may include, for example, a flip-flip, responsive to rotation of the photoreceptor drum, or some other two stage device. The drive rim or wheel 24 has included thereon an indicator 25 which, with each rotation of the photoreceptor drum, to which the drive rim 24 is connected, passes a sensing means 26, which may be a proximity sensor or any other type of sensor which may provide a pulse when the indicator 25 is in close alignment with the sensing means. The pulse may be transmitted to the cyclic controller 20 via the line 30. The flip-flop or two stage device in the cyclic controller may be driven back and forth from one state to the other state in response to a succession of pulses, each pulse indicating one rotation of the photoreceptor drum and the donor roller. Thus, the cyclic controller may be made responsive to the rotational position of the photoreceptor drum and donor roller on a two rotational cycle basis.

The phase 1 output of the cyclic controller 20, represented by line 32, extends to the corona charging corotron C for driving the relatively low corona charging function. The phase 2 output, represented by line 35, extends to the corona charging corotron C for driving the relatively highcorona charging function; to the illuminating apparatus D for operating the illuminating apparatus; to the toner-bath tray M for removing the tray from position where the donor roller rotates through the toner bath; to the decharge corotron L for removing the charge on the toner to be removed from the surface of the donor roller and to the transfer apparatus F for operating the transfer apparatus only after the latent image has been developed into a visible image. V

During the first rotation of the photoreceptor drum and the donor roller of the cycle of operation the corona charge placed on the entire surface of the photoreceptor drum is greater in magnitude than the magnitude of spurious and dissipated charges found on the background of the latent image on second rotation of the photoreceptor drum and donor roller so that spurious charges left within the dissipated charges found on the background will not falsely attract and/or capture any toner from the layer of toner on the drum roller and therefore maintain the background of the developed image clear. In addition, since the photoreceptor drum and the donor roller are substantially identical in diameter and both are driven at the same speed, the surfaces of each of the two cylinders will pass by each other in duplicated pattern for each rotation. This reduces the tight spacing tolerance normally required when out-of-contact development techniques are used.

The first rotation of the cycle of operation of the photoreceptor drum and the donor roller may be referred to as a dummy pass or a bias pass and the second phase or rotation of thecycle of operation may be referred to as the electrostatic copy forming pass or copy pass. The rotational sensor 26 may be mechanical, electrical or electronic and the cyclic controller correspondingly may be mechanical, electrical or electronic. The rotational position indicator may be any component to which the rotational sensor 26 will respond.

In an alternative arrangement of the present invention the corotron C may be a single corotron providing a uniform corona charge on the surface of the photoreceptor drum during both phases of the cycle and the illumination system D may be a dual functioning component which, during phase 1, is operated to provide a uniform level of illumination over the entire corona charged surface of the photoreceptor drum thus stimulating background illumination. This would effectively dissipate the corona charge on the surface of the photoreceptor drum so as to capture toner in the nonuniform layer of toner on the surface of the donor roller which would be captured by the background of the latent image during the next phase if such toner had not been previously removed. I

During phase 2, the surface of the photoreceptor drum would be corona charged with the same charge as in phase 1 but the illuminating system would function to illuminate the corona charged surface with a desired pattern of illumination thus forming the latent image on the surface of the photoreceptor drum. Development of the latent image'would then take place.

One embodiment of the present invention having been shown and described, an alternate arrangement having been described and some alternate apparatus having been mentioned other substitutions or changes may be made, as will be familiar to those skilled in the art without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

1. An electrostatic recording apparatus having means to generate an electrostatic latent image on an electrostatic image bearing surface and to develop the said latent image into avisible image, said electrostatic recording apparatus including;

photoreceptor means having a surface capable of holding an electrostatic charge,

toner layer bearing means having a surface capable of generating a layer of toner thereon when toner is applied to said surface,

toner supply means for supplying toner to said toner layer bean'ng means,

said photoreceptor means surface and said toner layer bearing means surface being substantially corresponding in dimensions,

means for applying an electrostatic charge of first power level onto the surface of said photoreceptor,

means for bringing corresponding parts of said photo-receptor means surface and said toner layer bearing means surface together in close proximity for removing predetermined portions of the layer of toner from the surface of said toner layer bearing means to the surface of said photoreceptor means for forming a uniform layer of toner on said surface of said toner layer bearing means,

means for cleaning the said surface of said photoreceptor means of said toner,

means for applying an electrostatic charge of second power level onto the surface of said photoreceptor means,

means for forming a latent image on the surface of said photoreceptor means by dissipating portions of the electrostatic charge of second power level in accordance with a predetermined pattern, and

said means for bringing corresponding parts of said photoreceptor means surface and said toner layer bearing means surface in close proximity also bringing said latent image and toner layer bearing surface adjacent one another for developing the latent image on the surface of said photoreceptor means into a visible image with toner from said uniform layer of toner.

2. An electrostatic recording apparatus as in claim 1 and further including means for transferring said visible image to a substrate for preserving said visible image.

3. An electrostatic recording apparatus as in claim 1 and in which said second power level of electrostatic charge is substantially greater in magnitude than said first power level.

4. An electrostatic recording apparatus as in claim 1 and in which said first power level is substantially 70 to 100 volts direct current, and

said second power level is substantially 400 to 500 volts direct current.

5. An electrostatic recording apparatus as in claim 1 and further including means for sensing when the corresponding parts of said photoreceptor means surface and said toner layer bearing means surface have been brought into close proximity.

6. An electrostatic recording apparatus including a photoreceptor drum and a donor roller each rotated uniformly and operating in a two rotation cycle of operation for generating a uniform layer of toner on the donor roller during the first rotation of the cycle and during the second rotation for generating a latent image and developing the latent image into a visible image employing the uniform layer of toner generated on the donor roller during the first rotation of the cycle of operation, said electrostatic recording apparatus including means for rotating said photoreceptor drum and said donor roller uniformly at the same speed of rotatron,

control means responsive to rotation of the rotating members for providing a first output for controlling one phase of the cycle of operation and for providing a second output for controlling the other phase of the cycle of operation,

means for supplying toner to the surface of said donor roller for generating a layer of toner on the surface of said roller during said one phase of the cycle of operation, and

means for generating an electrostatic charge of first magnitude during said one phase and for distributing said electrostatic charge on the surface of said photoreceptor so that as said photoreceptor drum and said donor roller rotate during said one phase the surface having said electrostatic charge of first magnitude will pass over the surface having said layer of toner and predetermined portions of toner from said layer of toner will be captured by said electrostatic charge of first magnitude and thereby create a uniform layer of toner on the surface of the donor roller.

7 An electrostatic recording apparatus as in claim 6 and further including means for cleaning the toner so captured by the electrostatic charge of first magnitude from the surface of the photoreceptor drum.

8. An electrostatic recording apparatus as in claim 6 and further including means for generating an electrostatic charge of second magnitude during said other phase of said cycle of operation and for distributing said electrostatic charge on the surface of said photoreceptor, means for illuminating the surface of said photoreceptor having said electrostatic charge of said second magnitude with a predetermined pattern for selectively dissipating the charges of said second magnitude for forming a latent image on said surface of said photoreceptor drum in accordance with such illumination.

9. An electrostatic recording apparatus as in claim 8 and in which said photoreceptor drum and said donor roller are positioned so that a portion of the surface of each are in close proximity and the said latent image is developed into a visible image as the photoreceptor drum and the donor roller rotate past each other.

10. An electrostatic recording apparatus as in claim 9 and further including substrate means selectively operated during said other phase of said cycle of operation for effectively transferring said visible image from the surface of said photoreceptor drum to a substrate for forming a permanent record.

11. The method of making an electrostatic copy of a desired pattern employing a photoreceptor means and a toner-donor means in which the photoreceptor means and the toner-donor means are sequenced through a cycle of operation including the steps of:

loading the surface of the toner-donor means with a layer of toner,

depositing a relatively low power electrostatic charge on the surface of the photoreceptor means, bringing the surface of the toner-donor means with said layer and the surface of the photoreceptor means with said relatively low power electrostatic charge in sufficiently close proximity to each other so that the ununiform portions of the layer of toner on the toner-donor means will be captured by the low power electrostatic charge on the photoreceptor means to provide a uniform layer of toner on the surface of the toner-donor means, depositing a relatively high power electrostatic charge on the surface of the photoreceptor means,

illuminating the surface of the'photoreceptor having the high power electrostatic charge with a desired pattern for forming a latent image on the surface of the photoreceptor means bringing the surface of the toner-donor means with the uniform layer of toner and the surface of the photoreceptor means with the latent image in sufficiently close proximity to each other to capture toner from the uniform layer in accordance with the electrostatic charges on the surface of the photoreceptor means for developing the latent image into a visible image and transferring the visible image onto a substrate for making a copy of the desired pattern.

12. A method of making an electrostatic copy of a desired pattern employing a photoreceptor drum and a toner-donor roller in which the photoreceptor drum serves as a biased roller for smoothing out a layer of toner on the toner-donor roller and then serves as a photoreceptor on which an electrostatic latent image is generated and the latent image is developed with the smoothed layer of toner on the surface of the tonerdonor roller including the steps of:

rotating the photoreceptor drum and the tonerdonor roller about their respective axis in a two rotation cycle of operation,

loading toner onto the surface of the toner-donor roller during the first rotation,

placing a low corona charge on the surface of the photoreceptor drum during the first rotation,

rotating the toner loaded surface and the low corona charged surface past each other so that the low corona charged surface captures non-uniform portions of toner on the layer of toner and forms a uniform layer of toner,

cleaning the toner so captured by the low corona charged surface,

placing a relatively high corona charge on the surface of the photoreceptor drum during the second rotation, illuminating the high corona charged surface with a desired pattern to form a latent image'- during the second rotation, and

developing-the latent image into a visible image with the uniform layer of toner during the second rotatron.

13. A method of making an electrostatic copy of a desired pattern as in claim 12 and further including the steps of:

transferring the developed image onto a substrate to preserve the visible pattern during the second rotation, and

cleaning the surface of the photoreceptor drum of all remaining toner after transfer.

14. In an electrostatic recording device for creating a copy of a predetermined pattern employing a photoreceptor surface for forming an electrostatic latent image and developing the latent image by presenting a layer of toner to the surface bearing the latent image by using a toner donor surface, the electrostatic recording device operating in a two-phase cycle of operation said device including means for generating a uniform electrostatic charge on the surface of the photoreceptor of a first magnitude during the first phase of the cycle of operation, means for loading a layer of toner on the surface of the toner donor during the first phase of the cycle of operation,

means for bringing the surface of the photorecepto having the uniform electrostatic charge thereon adjacent the surface of the toner-donor having the layer of toner thereon during the first phase of the cycle of operation,

means for generating an electrostatic charge latent image of the predetermined pattern on the surface of the photoreceptor during the second phase of the cycle of operation,

said means for bringing said surfaces adjacent one another also bringing the surface of the photoreceptor having the electrostatic latent image thereon adjacent the toner-donor surface having the layer of toner thereon during the second phase of the cycle of operation for developing the latent image and cyclic control means enabling the charged photoreceptor surface to remove excess toner from the layer on the toner-donor surface during the 12 first phase of the cycle of operation and for enabling said latent image generating means to generate a latent image on the surface of the photoreceptor during the second phase of the cycle of operations. v 15. in an electrostatic recording device as in claim 14 and in wh'ch the means f0 ene atin a uniform electrostatrc c arge on the surfae o the iihotoreceptor of a first magnitude includes a corotron for generating a corona charge and distributing said corona charge over the surface of said photoreceptor, and

means for illuminating the entire surface of said photoreceptor so charged for uniformly reducing the level of the charge on the surface of the photoreceptor to said first magnitude.

16. In an electrostatic recording device as in claim 14 and in which the means for generating an electrostatic charge on the surface of the photoreceptor of a first magnitude includes a first corotron for generating a corona charge of said first magnitude.

17. In an electrostatic recording device for creating a copy of a predetermined pattern employing a photoreceptor surface for forming an electrostatic latent image and developing the latent image by presenting a layer of toner to the surface bearing the latent image by using a toner-donor surface, the electrostatic recording device operating in a two-phase cycle of operation, said device including a first corotron for generating an electrostatic corona charge and for uniformly distributing a charge of first magnitude on the surface of the photoreceptor during the first phase of the cycle of operation,

means for loading a layer of toner on the toner-donor surface during the first phase of the cycle of operation,

means for bringing the surface of the photoreceptor having the uniform charge thereon adjacent the toner-donor surface having the layer of toner thereon during the first phase of the cycle of operation, and t means for generating an electrostatic charge latent image of the predetermined pattern on the surface of the photoreceptor during the second phase of the cycle of operation including a second corotron for generating an electrostatic corona charge and for distributing a charge of second magnitude on the surface of the photoreceptor and means for illuminating the surface so charged with a pattern of light for selectively dissipating the charge of second magnitude for forming said latent image.

said means for bringing said surfaces adjacent one another also bringing the surface of the photoreceptor having the latent image thereon adjacent the toner-donor surface having the layer of toner thereon during the second phase of the cycle of operation to develop the latent image. 

2. An electrostatic recording apparatus as in claim 1 and further including means for transferring said visible image to a substrate for preserving said visible image.
 3. An electrostatic recording apparatus as in claim 1 and in which said second power level of electrostatic charge is substantially greater iN magnitude than said first power level.
 4. An electrostatic recording apparatus as in claim 1 and in which said first power level is substantially 70 to 100 volts direct current, and said second power level is substantially 400 to 500 volts direct current.
 5. An electrostatic recording apparatus as in claim 1 and further including means for sensing when the corresponding parts of said photoreceptor means surface and said toner layer bearing means surface have been brought into close proximity.
 6. An electrostatic recording apparatus including a photoreceptor drum and a donor roller each rotated uniformly and operating in a two rotation cycle of operation for generating a uniform layer of toner on the donor roller during the first rotation of the cycle and during the second rotation for generating a latent image and developing the latent image into a visible image employing the uniform layer of toner generated on the donor roller during the first rotation of the cycle of operation, said electrostatic recording apparatus including means for rotating said photoreceptor drum and said donor roller uniformly at the same speed of rotation, control means responsive to rotation of the rotating members for providing a first output for controlling one phase of the cycle of operation and for providing a second output for controlling the other phase of the cycle of operation, means for supplying toner to the surface of said donor roller for generating a layer of toner on the surface of said roller during said one phase of the cycle of operation, and means for generating an electrostatic charge of first magnitude during said one phase and for distributing said electrostatic charge on the surface of said photoreceptor so that as said photoreceptor drum and said donor roller rotate during said one phase the surface having said electrostatic charge of first magnitude will pass over the surface having said layer of toner and predetermined portions of toner from said layer of toner will be captured by said electrostatic charge of first magnitude and thereby create a uniform layer of toner on the surface of the donor roller.
 7. An electrostatic recording apparatus as in claim 6 and further including means for cleaning the toner so captured by the electrostatic charge of first magnitude from the surface of the photoreceptor drum.
 8. An electrostatic recording apparatus as in claim 6 and further including means for generating an electrostatic charge of second magnitude during said other phase of said cycle of operation and for distributing said electrostatic charge on the surface of said photoreceptor, means for illuminating the surface of said photoreceptor having said electrostatic charge of said second magnitude with a predetermined pattern for selectively dissipating the charges of said second magnitude for forming a latent image on said surface of said photoreceptor drum in accordance with such illumination.
 9. An electrostatic recording apparatus as in claim 8 and in which said photoreceptor drum and said donor roller are positioned so that a portion of the surface of each are in close proximity and the said latent image is developed into a visible image as the photoreceptor drum and the donor roller rotate past each other.
 10. An electrostatic recording apparatus as in claim 9 and further including substrate means selectively operated during said other phase of said cycle of operation for effectively transferring said visible image from the surface of said photoreceptor drum to a substrate for forming a permanent record.
 11. The method of making an electrostatic copy of a desired pattern employing a photoreceptor means and a toner-donor means in which the photoreceptor means and the toner-donor means are sequenced through a cycle of operation including the steps of: loading the surface of the toner-donor means with a layer of toner, depositing a relatively low powEr electrostatic charge on the surface of the photoreceptor means, bringing the surface of the toner-donor means with said layer and the surface of the photoreceptor means with said relatively low power electrostatic charge in sufficiently close proximity to each other so that the ununiform portions of the layer of toner on the toner-donor means will be captured by the low power electrostatic charge on the photoreceptor means to provide a uniform layer of toner on the surface of the toner-donor means, depositing a relatively high power electrostatic charge on the surface of the photoreceptor means, illuminating the surface of the photoreceptor having the high power electrostatic charge with a desired pattern for forming a latent image on the surface of the photoreceptor means bringing the surface of the toner-donor means with the uniform layer of toner and the surface of the photoreceptor means with the latent image in sufficiently close proximity to each other to capture toner from the uniform layer in accordance with the electrostatic charges on the surface of the photoreceptor means for developing the latent image into a visible image and transferring the visible image onto a substrate for making a copy of the desired pattern.
 12. A method of making an electrostatic copy of a desired pattern employing a photoreceptor drum and a toner-donor roller in which the photoreceptor drum serves as a biased roller for smoothing out a layer of toner on the toner-donor roller and then serves as a photoreceptor on which an electrostatic latent image is generated and the latent image is developed with the smoothed layer of toner on the surface of the toner-donor roller including the steps of: rotating the photoreceptor drum and the toner-donor roller about their respective axis in a two rotation cycle of operation, loading toner onto the surface of the toner-donor roller during the first rotation, placing a low corona charge on the surface of the photoreceptor drum during the first rotation, rotating the toner loaded surface and the low corona charged surface past each other so that the low corona charged surface captures non-uniform portions of toner on the layer of toner and forms a uniform layer of toner, cleaning the toner so captured by the low corona charged surface, placing a relatively high corona charge on the surface of the photoreceptor drum during the second rotation, illuminating the high corona charged surface with a desired pattern to form a latent image during the second rotation, and developing the latent image into a visible image with the uniform layer of toner during the second rotation.
 13. A method of making an electrostatic copy of a desired pattern as in claim 12 and further including the steps of: transferring the developed image onto a substrate to preserve the visible pattern during the second rotation, and cleaning the surface of the photoreceptor drum of all remaining toner after transfer.
 14. In an electrostatic recording device for creating a copy of a predetermined pattern employing a photoreceptor surface for forming an electrostatic latent image and developing the latent image by presenting a layer of toner to the surface bearing the latent image by using a toner donor surface, the electrostatic recording device operating in a two-phase cycle of operation said device including means for generating a uniform electrostatic charge on the surface of the photoreceptor of a first magnitude during the first phase of the cycle of operation, means for loading a layer of toner on the surface of the toner donor during the first phase of the cycle of operation, means for bringing the surface of the photoreceptor having the uniform electrostatic charge thereon adjacent the surface of the toner-donor having the layer of toner thereon during the first phase of the cycle of operation, means for generating an electrostatic charge latent image of the predetermined pattern oN the surface of the photoreceptor during the second phase of the cycle of operation, said means for bringing said surfaces adjacent one another also bringing the surface of the photoreceptor having the electrostatic latent image thereon adjacent the toner-donor surface having the layer of toner thereon during the second phase of the cycle of operation for developing the latent image and cyclic control means enabling the charged photoreceptor surface to remove excess toner from the layer on the toner-donor surface during the first phase of the cycle of operation and for enabling said latent image generating means to generate a latent image on the surface of the photoreceptor during the second phase of the cycle of operations.
 15. In an electrostatic recording device as in claim 14 and in which the means for generating a uniform electrostatic charge on the surface of the photoreceptor of a first magnitude includes a corotron for generating a corona charge and distributing said corona charge over the surface of said photoreceptor, and means for illuminating the entire surface of said photoreceptor so charged for uniformly reducing the level of the charge on the surface of the photoreceptor to said first magnitude.
 16. In an electrostatic recording device as in claim 14 and in which the means for generating an electrostatic charge on the surface of the photoreceptor of a first magnitude includes a first corotron for generating a corona charge of said first magnitude.
 17. In an electrostatic recording device for creating a copy of a predetermined pattern employing a photoreceptor surface for forming an electrostatic latent image and developing the latent image by presenting a layer of toner to the surface bearing the latent image by using a toner-donor surface, the electrostatic recording device operating in a two-phase cycle of operation, said device including a first corotron for generating an electrostatic corona charge and for uniformly distributing a charge of first magnitude on the surface of the photoreceptor during the first phase of the cycle of operation, means for loading a layer of toner on the toner-donor surface during the first phase of the cycle of operation, means for bringing the surface of the photoreceptor having the uniform charge thereon adjacent the toner-donor surface having the layer of toner thereon during the first phase of the cycle of operation, and means for generating an electrostatic charge latent image of the predetermined pattern on the surface of the photoreceptor during the second phase of the cycle of operation including a second corotron for generating an electrostatic corona charge and for distributing a charge of second magnitude on the surface of the photoreceptor and means for illuminating the surface so charged with a pattern of light for selectively dissipating the charge of second magnitude for forming said latent image. said means for bringing said surfaces adjacent one another also bringing the surface of the photoreceptor having the latent image thereon adjacent the toner-donor surface having the layer of toner thereon during the second phase of the cycle of operation to develop the latent image. 